According to Goal sources, the Australian centre-back was on the verge of joining Jeonbuk Motors or Buriram United in the lead-up to this season but a combination of red tape and Adelaide's reticence to let him go meant he stayed at Coopers Stadium for a third year.

The 25-year-old played 82 A-League games during his time at Adelaide and was a key figure in the Reds premiership-championship double of 2015-16, while he also won the 2014 FFA Cup.

"It's a high quality league and I'll be playing against some huge clubs. On the weekend I went to watch them against Porto and there's obviously Benfica and Sporting Lisbon, too - Champions League and Europa League clubs, so that'll be exciting for me to play against that quality of opposition."

Pacos is the former home of Socceroos left-back Jason Davidson, who played five Primeira Liga games there from 2009 to 2012.

McGowan confirmed that he could have left Adelaide a year ago for a club in Asia but indicated he preferred a European move to improve his chances of breaking into the Socceroos.

But Goal understands he would have joined Jeonbuk last year if they could have offloaded former Melbourne City midfielder Erik Paartalu before the mid-season transfer window in the K League had closed.

Thai League giants Buriram were also very keen on McGowan and even discussed paying a transfer fee to secure his services but Adelaide's reticence to lose another senior player heading into their title defence effectively closed that door.

Pacos sits 14th in Portugal's 18-team top division with one game remaining this season but finished third as recently as 2012-13.